Multiple cycle tidal regenerator engine

ABSTRACT

A tidal regenerator heat engine using separate condensable vapors as working fluids in each of two or more interconnected single cycle tidal regenerator heat engines. Cyclic condensation and evaporation of the working fluids takes place in a controlled manner in the respective ones of variable liquid level regenerators in the single cycle component engines. A first working fluid having a relatively low vapor pressure is successively heated, vaporized at constant pressure, and condensed in part at constant volume and in part at constant pressure. The heat extracted during condensation provides input heat to a second working fluid having a relatively high vapor pressure which is successively heated, vaporized at constant pressure, superheated, cooled at constant volume, condensed in part at constant volume and in part at constant pressure. The heat required for the second low temperature working fluid cycle is provided from the heat rejected by the first high temperature working fluid cycle.

United States Patent [191 Huffman et al.

[111 3,815,363 [451 June 11, 1974 MULTIPLE CYCLE TIDAL REGENERATOR ENGINE [75] Inventors: Fred N. Huffman, Sudbury; Kenneth G. Hagen, Acton, both of Mass.

[73] Assignee: Thermo Electron Corporation,

Waltham, Mass. [22] Filed: Jan. 15, 1973 [21] Appl. No.: 323,889

[52] US. Cl... 60/531, 60/38 [51] Int. Cl. F03g 7/06 [58] Field of Search 60/38, 25; 417/379; 91/4 [56] References Cited UNITED STATES PATENTS 3.IOO,965 8/1963 Blackburn; 91/4 3,487,635 l/l9 70 Prast et al 60/24 3,608,31 l 9/l97l Roesel 60/1 FOREIGN PATENTS OR APPLICATIONS 125,395 ll/l920 Great Britain 60/38 247,546 3/1926 Great Britain 60/38 423,662 2/1935 Great Britain (50/323 Primary Examiner-Edgar W, Geoghegan Assistant Examiner-H. Burks, Sr. Attorney, Agent, or Firm-James 1L. Neal 5 7] ABSTRACT A tidal regenerator heat engine using separate condensable vapors as working fluids in each of two or more interconnected single cycle tidal regenerator heat engines. Cyclic condensation and evaporation of the working fluids takes place in a controlled manner in the respective ones of variable liquid level regenerators in the single cycle component engines. A first working fluid having a relatively low vapor pressure is successively heated, vaporized at constant pressure, and condensed in part at constant. volume and in part at constant pressure. The heat extracted during condensation provides input heat to a second. working fluid having a relatively high vapor pressure which is successively heated, vaporized at constant pressure, superheated, cooled at constant volume, condensed in part at constant volume and in part at constant pressure. The heat required for the second low temperature working fluid cycle is provided from the heat rejected by the first high temperature working fluid cycle.

14 Claims, 11 Drawing Figures TEMPERATURE ENGINE PATENTEDJuun 1974 33315363 SHEET 10F 7 /29 I HIGH I TEMPERATURE L LOW TEMPERATURE ENGINE I ENGINE lo 50 4o.

PATENTEDJUN H mm 21815363 sum 2 BF 1 MERCURY CONST. PRESSURE TEMPERATURE STEAM ENTROPY FIG. 2

Pmmsmun 11 mm 38151363 SHEET 3 OF 7 FIG. 3B BEGlN POWER STROKE FIG. 3A END RETURN STROKE BACKGROUND OF THE INVENTION This invention relates to heat engines and more particularly to a multiple cycle tidal regenerator heat engme.

Stirling cycle heat engines have been known in the art for many years. Such engines repetitively contract and compress a given quantity of gas at a low temperature and expand that gas at a high temperature toproduce network output. However, such engines are com mercially impractical because of the extremely high operating temperatures which are necessary for the production of reasonable level of output power.

More practical heat engines have been designed from derivatives of the basic Stirling cycle configuration, modified by substituting a condensable vapor for the gas as the working fluid. Such engines incorporate a variable liquid level, or tidal, regenerator and an associated displacement piston for selectively transferring the working fluid from a condenser sector at one end to a vaporizer sector at the opposite end of the tidal regenerator. As the working fluid is transferred between the two sectors of the tidal regenerator, heat is stored or supplied by the tidal regenerator, and net work output is derived from a power piston which is actuated by the substantial difference (relative to a gas cycle engine such as the basic Stirling cycle engine) between vaporizer and condenser pressure. A single cycle tidal regenerator engine of this type. is disclosed in US. Pat. No. 3,657,877, assignedto, the assignee of the present invention and application. The single cycle tidal regenerator engine is, howevensomewhat limited in efficiency by the relatively small difierence between the mean effective temperature at which heat may be added to the cycle and the mean effective temperature at which the heat is removed. The theoretical efficiency value for a single cycle tidal regenerator engine is of the order of 9- 12 percent, the variation being related tothe degree artimiztidiBfiEETjEred heat iii the regeneration process.

It is further known in the art to elevate the mean effective heat input temperature of a vapor cycle engine toward the metallurgical limit of the structural materials by selecting a working fluid having a substantially low vapor pressure, such as mercury, thereby allowing a substantial portion of the heat of a cycle to be added at a relatively high temperature. However, during the cooling portion of an engine cycle, such working fluids reach a substantially low pressure at a relatively high temperature. As a result, the difference between the effective source and sink temperatures remains small, precluding an improvement in efficiency compared with engines using higher vapor pressure working flu.- ids. However, the heat rejected by a cycle using a low vapor pressure working fluid has been utilized as a heat input to a second cycleus'ing a suitable workingfluid, such as steam, which can provide a matching pressure range, but has temperatures below the heat rejection temperatures of the mercury (or topping) cycle. This binary Rankine cycle concept has been reduced to practice in central power station application but proved to be commercially impractical because of the difficulties encountered in adequately containing mercury within conventional equipment, the associated erosion of turbine buckets, and the reliability problems associated with bearings, seals, and feed pumps, these reliability problems being primarily due to operation in a very hot mercury environment. Further difficulties have been encountered due to the generally increased complexity of the total system.

The tidal regenerator engine described in the above cited US. Pat. No. 3,657,877 is a simple and fundamentally reliable engine, and uses few components of the type which create complexities encountered in the binary cycle Rankine engines. 7

SUMMARY OF THE INVENTION Accordingly, it is a principal object of this invention to improve tidal regenerator engines through the use of two or more cascaded, coupled cycles.

Another object is to increase substantially the efiiciency of heat engines.

A further object is to increase substantially the reliability of heat engines.

Still another object is a new and improved heat engine in which heat is added to the cycle at a substantially increased average temperature.

In the present invention, a tidal regenerator engine configuration is modifiedby cascading two tidal regenerator engines so that a first engine operates at relatively high temperature and provides either the entire or a substantial portion of the heat input of a second engine operating at a relatively low temperature. Each component engine has a separate working fluid with the first such component engine using a working fluid having a'relatively low vapor pressure (hereinafter referred to as high temperature wotkingfluidL-and the second component engine utilizes a working fluid having a relatively high vapor pressure (and hereinafter referred to as the low temperature working fluid).

In the present invention, the high temperature working fluid is heated and vaporized at constant pressure during which stage work is extracted. The high temperature working fluid is then condensed in part at constant volume and in part at constant pressure. The heat extracted during the condensation portion of the cycle serves as the heat input to the low temperature working fluid cycle. In this low temperature working fluid cycle, the working fluid is successively heated, vaporized at constant pressure, superheated, cooled at constant volume and then condensed in part at constant volume and in part at constant pressure. Work is extracted during the constant pressure vaporization and superheat ing. The two component engines are configured and phased so that each additively contributes to the combined net work output of the composite binary cycle engine. The quantities of low and high temperature working fluids and engine configuration are so selected that the amount of heat rejected by the condensation portion of the high temperature cycle is precisely that amount of heat required by the heating portion of the low temperature cycle. The theoretical efficiency of this binary cycle tidal regenerator engine is approximately 20 percent, a considerable improvement over the theoretical efficiency of the ideal single cycle tidal regenerator engine which runs about 9 percent.

As with the single cycle tidal regenerator engine, further efficiency improvement is obtained through the use of regenerators which are effective to store the heat extracted from the condensation portions of each cycle and to utilize this heat in the respective heating portions of the cycle. This regeneration of heat is accomplished in both the high and low temperature cycles. In addition, in the low temperature cycle, the heat rejected during the cooling of the superheated low temperature working fluid may be regenerated to provide a portion of the superheat needed in the superheating portion of that cycle. The overall effect of the regeneration provides for theoretical efliciency values as high as 27 percent for the binary cycle tidal regenerator engine compared to the 12 percent figure for the single cycle tidal regenerator engine operating at similar pressure and temperature conditions. Much of the overall increased efficiency in the binary cycle tidal regenerator engine is due to the high average temperature at which heat is added to the high temperature working fluid cycle.

In addition to the above-described advantage of increased efficiency of the binary cycle tidal regenerator engine over the prior art, favorable characteristics of the single cycle tidal regenerator engine are retained. These include (I) the ability to obtain a high output pressure differential while maintaining a modest temperature differential, (2) elimination of mechanical valves, (3) elimination of the feed pump, (4) silent operation, (5) ease of coupling to a hydraulic load, (6) provision for both liquid and vapor regeneration, and (7) adaptability to a variety of working fluids (including mixed working fluids).

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects of this invention, the various features thereof, as well as the invention itself, may be more fully understood from the following description when read together with the accompanying drawings, in which:

FIG. 1 is a semi-schematic view of a heat engine in accordance with the present invention;

FIG. 2 is an idealized temperature-entropy diagram of the binarycycle tidal regenerator heat engine;-

FIGS. 3A 3H are outlined drawings of the operational stages of an engine in accordance with the present invention; and

FIG. 4 is an outline drawing of a practical tidal regenerator engine incorporating the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1,. there is shown a simple form of a binary cycle tidal regenerator heat engine 5 embodying the present invention. The engine 5 is a composite structure having two component single cycle tidal regenerator engines including a low temperature working fluid component engine 10, and a high temperature working fluid component engine 40. The engines 10 and 40 may be characterized by an input and output temperature, respectively corresponding to the temperature at which heat is added and rejected. It will be understood that the ranges of temperature between the input and output temperatures for each of the engines are nonoverlapping and the range for the engine 40 includes temperatures higher than the range for the engine 10. The engine 10 includes a displacement cylinder 12, a condenser 14, a tidal regenerator 16, a vaporizer 18, a superheater 22 and a power cylinder 24. The tidal regenerator 16 is a cylindrical structure having successive levels of heat-retaining elements. each level maintaining a substantially constant characteristic temperature.

4 A displacement piston 26 is reciprocatory within the displacement cylinder 12 in response to an appropriate force supplied via a mechanical linkage 28 from a drive assembly 29. A fluidic output portion of the cylinder l2 is connected to the condenser 14 which in turn is disposed at a lower end of the tidal regenerator 16. The vaporizer 18 communicates with the upper end of the tidal regenerator l6 and has an outlet connected to the superheater 22. The superheater 22 had dual outlets 22a and 22b, the first of which, 22a, is connected to an inlet to the power cylinder 24. The second outlet, 22b, of the superheater 22 is connected to an inlet of the high temperature working fluid engine 40, as described below. A power piston 32 is arranged for reciprocating motion within the power cylinder 24. Both the displacement piston 26 and the power piston 32 are provided with conventional peripheral members to assure a leak-proof seal between the pistons and their respective cylinder walls. The fluidic output of the cylinder 24, contributes through a line 24a of the binary cycle tidal regenerator engine 5 as explained in greater detail below.

A low temperature working fluid 36 is disposed within the engine 10 in the region of that engine above the piston 26. An output fluid 38 for the binary cycle tidal regenerator engine 5 is disposed in the region of the engine below the power piston 32 and in the fluidic line 24a and in an output fluidic line 5a of the engine 5. a

The condenser 14 and the vaporizer 18, in which heat is respectively extracted from and applied to the working fluid, as indicated by the symbols Q0141 Qim are arranged so as to establish a temperature gradient across the successive levels of heat-retaining elements of the tidal regenerator 16. The quantity of low temperature working fluid 36 in the engine 10 is such that when the piston 26 is in its minimum height position, the surface level of the fluid 36 is located within condenser 14. The dimensions of the structure and the quantity of fluid 36 are further related so that when the piston 26 is at its maximum height position, the level of the working fluid lies within the vaporizer 18.

The operation of the low temperature engine 10 will now be explained in broad terms in conjunction with FIGS. 1 and 2, with detailed operation being described below in conjunction with FIG. 3. It will be understood that FIG. 2 refers to an embodiment using steam as a low temperature working fluid and mercury as a high temperature working fluid for the respective component engines. As explained below, the use of steam as the low temperature working fluid and mercury as the high temperature working fluid is merely for illustrative purposes, the present invention not being limited to those working fluids.

Starting from an initial position of piston 26 in its minimum height position (point a in FIG. 2), in response to which the level of the working fluid 36 lies within the condenser 14, the vapor pressure above the fluid 36 within the engine 10 is at a minimum level and the piston 32 lies atits maximum height position within the cylinder 24. For the purposes of this broad description of the operation of the engine 10, the second outlet 22b of the superheater 22 is assumed to be sealed.

In operation, the drive assembly 29 raises the piston 26 to its maximum height position in the cylinder 12 and in response thereto, the level of the working fluid is raised to the vaporizer 18. Heat is added to the working fluid 36 in vaporizer l8 and the temperature of the fluid 36 is raised to the temperature of vaporization of the fluid 36 (path a-b' in FIG. 2). As heat continues to be added in the vaporizer 18, an increasing portion of the working fluid 36 vaporizes. As the volume of the working fluid vapor increases, the piston 32 is displaced in a downward direction within the cylinder 24 so that the pressure within the engine 10 remains constant (path b"c in FIG. 2.) Thus, work is extracted 'at constant pressure during this portion of the cycle of operation resulting in a net force being applied to the hydraulic fluid 38 within the fluidic lines 24a and 5a representing the binary cycle engine 5 output. To achieve a substantial high operating efficiency of the engine 10, the vapor in the engine 10 is then superheated by the superheater 22 (path c-d in FIG. 2), producing an additional pistondisplacement which in turn produces a further component of work outputrAt such time, when the power piston 32 is at its minimum height position, having transferred the net work of engine 10 to the output line 5a, the assembly 29 is then effective to drive the piston 26 to its minimum height position. In response thereto, the level of the working fluid 36 is lowered to a point within the condenser 14. The working fluid vapor is thereby cooled at constant volume (path 11-3 in FIG. 2), and then the power piston 32 rises to its maximum height position in the cylinder 24, (path g-a in FIG. 2), while the working fluid is further condensed at constant pressure to complete a cycle of operation for the engine 10. This operation of engine 10 is thus substantially similar to the single cycle tidal regenerator engine disclosed in the above-cited US. Pat. No. 3,657,877.

Now, turning to the high temperature cycle engine 40, it may be seen in FIG. 1 that a displacement cylinder 42 is connected to a condenser 44, which in turn is connected by a tidal regenerator 46 to a vaporizer 48. The output of the vaporizer 48 is connected to the fluidic input of a power cylinder 52 whose output fluidic line 52a is connected to the hydraulic output line 5a of the binary cycle engine 5. The tidal regenerator 46 is also a cylindrical structure having successive levels of heat retaining elements, each level maintaining a substantially constant characteristic temperature. As with the displacement cylinder 12 of the engine 10, the cylinder 42 of the engine 40 contains a displacement piston 54 arranged for reciprocating motion within the cylinder 42 and having appropriate seals to prevent bypassing of the working fluid in the engine 40. In addition, the power cylinder 52 is arranged in a similar fashion to the power cylinder 24 in the engine 10; that is, the power piston 56 is arranged within the cylinder 52 in a manner such that the piston 56 may reciprocate therein, the piston 56 also having appropriate seals to prevent by-passing of the working fluid.

The component engine 40 is provided with a high temperature working fluid 58. The quantity of that fluid 58 which may be used in the engine is subject to two constraints. The first constraint relates the quantity of the fluid 58 to the dimensions of the engine 40 so that the level of the working fluid 58 lies within condenser 44 when the displacement piston 54 is in its minimum height position and the level lies within the vaporizer 48 when piston 54 is in its maximum height position. The second constraint on the quantity of working fluid 58 in the component engine 40, relating the engines 40 and 10, will be discussed below. The condenser 44 and vaporizer 48, for respectively extracting heat from and applying heat to the working fluid 58 (as indicated by the symbols 0' and 0' establish a temperature gradient acrossthe successive levels of heatretaining elements of the tidal regenerator 46.

In broad terms again, the operation of the component engine 40 will now be described in conjunction with FIGS. 1 and 2. Starting initially with the displacement piston 54 in its minimum height position (point 1 in FIG. 2), so that the surface level of the working fluid 58 is within the condenser 44, the above described second fluidic output line 22b from the super-heater 22 provides a displacement force on the piston 54. This force is produced by the constant pressure displacement of the working fluid 36 in the engine 10, occurring, as described above, in response to the displacement of the piston 26 to its maximum height position.

The piston 54 is displaced by this applied force to its maximum height position so that the surface level of the working fluid 58 is within the vaporizer 48. The working fluid 58 is heated to its vaporization point (path 1-2 in FIG. 2) as the fluid rises through the tidal regenerator 46 and by the application of heat in the vaporizer 48 (denoted in FIG. 1 by the symbol Q", adjacent to the vaporizer 48). As heat is continuously added in the vaporizer 48 at a substantially high temperature, an increasing portion of the high temperature working fluid 58 is vaporized.

In response to the increased vaporization of the working fluid 58, the piston 56 is displaced in a downward direction so that the vapor in the engine 40 undergoes an increase in volume (or expansion) while remaining at a constant pressure (path 2-3 in FIG. 2). As the piston 56 is displaced, work is; extracted from the binary cycle engine via the fluidic line 52a which is coupled to the output hydraulic line 5a. To assure that this work is added to that derived from the displacement of piston 32, the displacement piston drive assembly 29acts as a means for phasing the cycle for the low temperature engine 10 relative to the cycle for the high temperature engine 40 so that the displacement piston 26 of engine 10 is lowered from its maximum height position following the displacement of the power piston 56 to it minimum height position. As the displacement piston 26 returns to its minimum height position, the vapor pressure in the engine 10 is returned to a minimum level, as described above, during the period where the working fluid 36 is condensed at constant volume (path f-g in FIG. 2).

As the vapor pressure in the engine 10 decreases, the force applied to the displacement piston 54 via line 22b diminishes and that piston returns to its minimum height position, thereby lowering the level of the work ing fluid 58 so that the level of that fluid is within the condenser 44. This accomplishes a constant volume cooling of the vapor in the engine 40 (path 3-4 in FIG. 2). The power piston 56 then rises to its maximum height position during a constant pressure condensation of the vapor in the engine 40 (path 4-1 in FIG. 2)

to thereby complete a cycle of operation for the engine 40 and the composite binary cycle engine 5. In this manner, the work output of the two component engines 10 and 40 is added in phase during the power stroke to provide a combined hydraulic work output on the fluidic line 5a.

The above mentioned second constraint on the quantity of the working fluid 58 in the engine 40 may now be described. This second constraint relates the quantities of the working fluids 36 and 58 in the respective engines 10 and 40. During periods when the working fluid 58 level is at a point within the condenser 44, that condenser is effective to remove a quantity of heat from the fluid in that engine, as indicated in FIG. 1 by the symbol That extracted heat is transferred by the heat transfer means 60 to the vaporizer 18 for use as the input heat (denoted O in the engine 10. The amount of heat available from the heat transfer means 60 determines the maximum quantity of the working fluid 36 which may be used in the low temperature engine, since that quantity of heat must be sufficient to drive the engine 10 through its cycle. Thus all of the heat required for the low temperature cycle is obtained from the heat rejected from the high temperature cycle so that a maximum efficiency binary cycle engine is attained.

As with the single cycle tidal regenerator engine, regeneration techniques may be used to provide further efficiency improvement. Referring to FIG. 2, in the high temperature cycle, the heat added in process 12 may be regenerated from process 34. In the low temperature cycle, the heat rejected in process d-e can be regenerated to provide a portion of the superheat needed in process c-d. Similarly, the heat rejected between e and f can be used to partially regenerate b-b'. Finally, the heat added in process a-b can be regenerated from that rejected in process f-g. The overall effect of these regeneration processes allow a theoretical efficiency value for the binary cycle tidal regenerator engine to be as high as 27 percent compared with an efficiency of 12 percent for the single cycle tidal regenerator engine operating at similar pressure and temperature conditions.

The above described operating sequence for the engine may be more clearly understood by referring to FIGS. 3A-H, and FIG. 2. The somewhat modified engine configuration shown in FIG. 3 (reference to FIG. 3 includes FIGS. 3A-H is thermo-dynamically equivalent to that shown in FIG. 1. The reference numerals in the engine of FIG. 3 relate the corresponding parts in the engine of FIG. 1. It will be understood that heat transfer means 60 and symbols Qm Qmu, 0'1", 0' and Q",,,,,, as shown in FIG. 3A, are deleted for convenience from FIGS. 3B-l-I. Similarly the reference numerals of FIG. 3A will be understood to apply to the corresponding parts shown in FIGS.'3B-l-l. It will be noted that in FIG. 3 the isolation pistons 62, 64 and 66 provide for both thermal isolation and phase isolation between the liquid and vapor phases of the working fluids 36 and 58 and the additional fluids 68 and 69, which are used for isolation and to hydraulically couple the respective output isolation pistons 62 and 66 with the respective ones of the power pistons 54 and 56. The pressure balance lines 71 and 72 respectively provide for pressure equalization between the respective displacement and power cylinders of the engines and 40. It will be further noted that output cylinders 24 and 52 are interconnected via a valve system to couple the output of the engine 5 with the fluid output line 5a.

FIG. 3A shows the end of a return stroke of the power pistons 32 and 56, with those pistons in their maximum height position. This point will be taken as the starting point for the description of the engine 5 operation. In FIG. 3B, the electronic control 29a is shown to have caused the drive assembly 29 to move the displacement piston 26 to its maximum height position. This resultant motion raises the surface level of the working fluid 36 to a point within the vaporizer 18. Heat Q from the heat transfer means is added to the fluid 36 in vaporizer l8, raising the temperature of that fluid to the boiling point (path a-b" of FIG. 2). As additional heat is added from the heat transfer means 60, increasing portions of the fluid 36 vaporize. The resultant vapor undergoes the constant pressure expansion (path b'c of FIG. 2), causing the isolation pistons 62 and 64 to move in the indicated directions (FIG. 3B). The displacement piston 54 and the power piston 32, which are hydraulically coupled to the respective ones of the pistons 64 and 62, begin the power stroke of the engine 5 operation by moving in the indicated directions (FIG. 3B). As the piston 32 moves in the downward direction, the ball valves shown are effective to produce a fluid flow as indicated in the hydraulic line 5a. Thus, as the heat is continually added to the vaporizer 18, the isolation piston 62 and the power piston 32 continue in their downward direction, as shown in FIG. 3C. In addition, the isolation piston 64 and the displacement piston 54 move together as shown in FIG. 3C to displace the high temperature working fluid 58 so that the surface level rises through regenerator 46 and into vaporizer 48. Thereupon, the power stroke continues as shown in FIG. 3D with the isolation piston 62 and the power piston 32 continuing their downward motions toward their minimum height positions. During this portion of the cycle, heat, 0" is added to the superheater 22 and the superheater 22 provides additional expansion of the vapor from the working fluid 36 (path c-d of FIG. 2), this expansion being in response to heat applied at a substantial high temperature, and increasing the efficiency of the low temperature cycle. In addition, as shown in FIG. 3D, the vaporizer 48 is effective to bring the working fluid 58 to the vaporization temperature (path l2 of FIG. 2). As heat, 0' continues to be added to the vaporizer 48, the working fluid 58 is vaporized in increasing amounts. The increasing amounts of vapor expand at constant pressure by displacing the isolation piston 66 (path 23 of FIG. 2). The isolation piston 66 is hydraulically coupled to the power piston 56 and, thus, the pistons 66 and 56 move together in a downward direction to continue operation of the engine during the power stroke and provide an additive force component to the fluid output line 5a. As heat continues to be added in the respective ones of the vaporizers l8 and 48 and the superheater 22, the power pistons 32 and 56 and their re spective isolation pistons reach their extreme positions, thereby terminating the power stroke portion of the engine 5, as shown in FIG. 3E.

The return stroke commences, as shown in FIG. 3F with the electronic control 29a causing the drive assembly 29 to return the displacement piston 26 to its minimum height position. As the piston 26 is lowered, the surface level of the working fluid 36 is returned through the thermal regenerator 16 to a point within the condenser 14. Heat, O is extracted from the fluid 36 in this process and the vapor pressure in the engine 10 decreases. As the pressure decreases, the isolation piston 62 and the power piston 32 together with the isolation and the displacement pistons 54 and 64 return in the direction toward their initial starting points. The pistons move in the indicated directions as shown in FIG. 3F, with the result that the ball valves are operated so as to draw in new fluid in the hydraulic line a. The return stroke continues as shown in FIG. 3F.

As the displacement piston 54 lowers towards its minimum height position, that motion is accompanied by a corresponding drop in the surface level of the working fluid 58 from the vaporizer 48 through the tidal regenerator 46 and to a point in the condenser 44. Heat, Q' is extracted from the fluid 58 and the vapor from working fluid 58 is cooled at constant volume. As a result, the vapor pressure in the engine 40 decreases (path 34 in FIG. 2) and the isolation piston 66 and the power piston 56 are moved in the indicated directions toward their maximum height positions (path 4-1 in FIG. 2). As shown in FIG. 36, additional incoming hydraulic fluid is drawn into the power cylinder 52. As shown in FIG. 3H, the power pistons 32 and 56 together with their corresponding isolation pistons and also the displacement piston 54 return toward their initial positions to finally correspond to the positions shown in FIG. 3A, thereby ending the return stroke portionof the engine 5, operation. This last motion is accompanied by a constant pressure condensation of the respective working fluids 36 and 58 (paths g-a and 4-1 of FIG. 2). The operation cycle of the engine 5 is now complete and ready to be repetitively performed in response to an appropriate signal by the electronic control 29a.

A practical embodiment of the present invention is shown in FIG. 4. The tens and units digits of the reference numerals of FIG. 4 and of the following description relate the referenced parts in FIG. 4 to the corresponding elements of the engine shown in FIG. 3. All of the displacement and power pistons shown in FIG. 4 are of the bellows type, thereby eliminating possible leakage losses around a sliding piston assembly. Pressure equalization between the fluidic output line 105a and the piston 126 is achieved by a fluid diagram isolator 73 which is disposed between the hydraulic fluid 138 in the output line 105 and a pressure balancing fluid, such as Freon, in the interior sector of the bellows displacement piston 126. This embodiment, providing mechanical simplicity and efficiency of operation, is shown to use mercury as the high temperature working fluid and steam as the low temperature working fluid. Operation of the engine corresponds to the temperature-entropy diagram shown in FIG. 2. The use of mercury and steam as working fluids is merely for illustrative purposes, and the present invention is not limited to those working fluids. For example, Dowtherm A may also be used as a high temperature working fluid and Flurinol may be used as a low temperature working fluid. Similarly, other suitable materials may be used.

As shown in FIG. 4, an electronic control 129a controls the drive assembly 129, which in this embodiment is a DC torque motor for driving a ball screw which displaces a ball nut. The displaced ball nut is effective to drive the bellows displacement piston 126. In

10 tor 116 are successive layers of heat-retaining elements, such as metal wool. Within the vaporizer 118, there are disposed a quantity of braized balls for enlarging the hot surface area to obtain a highly efficient means for vaporizing the working fluid. The heat input to the vaporizer 118 is supplied via the fluidic line 81. As will be described in more detail below, the line 81 contains an isolation fluid 81a, comprising silicone oil, which is both thermally and hydraulically coupled to the bellows power piston 156. The silicone oil maintains the vaporizer l 18 at the approximate temperature 342 Fahrenheit.

The vaporizer 118 has a dual output for the passage of steam to the bellows power piston 156 (via line 122a) and to the superheater 122 (via line 122k). The

bellows power piston 156 provides the single power output piston which is driven by both the low temperature and high temperature component engines of the binary cycle engine of FIG. 4. The interior region of bellows power piston 156 contains silicone oil 81a, which is in turn routed through the fluidic line 81 to a mercury bellows displacement piston 154 and to an isolation cylinder 85. The cylinder 85 encloses a hollow thermal isthmus piston 87 which is hydraulically coupled by a fluid 88, such as silicone oil, to a bellows isolation piston 89. The piston 89 is directly coupled to the hydraulic output line 10511 of the engine 105.

The mercury bellows displacement piston 154 is disposed within cylinder 142. Mercury is used as the working fluid 158 in the region above piston 154. The cylinder 142 is in direct communication with the mercury condenser 144, which acts as a heat sink at approximately 576 Fahrenheit. An outlet of the cylinder 142 is connected via the mercury liquid/vapor regenerator 146 to the mercury vaporizer 148. The vaporizer 148 is maintained at an approximate temperature 935 Fahrenheit. The vaporizer 148 is also used as the superheater 122 for the low temperature engine portion of the engine 105. A bellows mercury vapor power piston is connected to the output of the vaporizer 148. That piston 165 is in communication with an isolation piston 166, which is arranged for reciprocal motion within the cylinder 167. The piston 166 is composed of a synthetic mica insulator and is in direct contact with the bellows power piston 156.

In operation, the DC torque motor 129 is actuated by the control 129a to drive the bellows displacement piston 126. The water 136 in the cavity above the bellows piston 126 is displaced through the steam condenser 114 and the tidal regenerator 116 so that the surface level is within the vaporizer 118. A small amount of water is vaporized immediately, with the resultant steam flowing out of the vaporizer 118 and dividing into two streams via the lines 122a and b. The first stream, passing via the line 1220, pressurizes the cavity external to the} bellows power piston 156, and the second stream flows, via theline 122b, through the superheater 122 and pressurizes the cavity between the super mica piston insulator 166 and the mercury bellows powerpiston 165. The resultant pressure applied to the bellows power piston 156 is transferred (via the silicone oil 81a within bellows 156) to the mercury bellows displacement piston 154. The transferred pressure is effective to expand the bellows piston 154. The displacement of the bellows 154 is in turn effective to push liquid mercury 158 through the condenser 144 and the tidal regenerator 146 tothe mercury vaporizer 148. Mercury vapor is generated in this vaporizer and that vapor passes to expand the mercury bellows power piston 165, displacing the synthetic mica piston 166. Concurrently, steam continues to be generated in the steam vaporizer 118. As the synthetic mica piston 166 is displaced by the expansion of the mercury power piston 165 and the superheated steam, the bellows power piston 156 is collapsed. The saturated steam surrounding this bellows piston is squeezed out via line 122a and through line 122b to the superheater 122, adding to the superheated steam which is already applying force to the synthetic mica piston 166 and collapsing the piston 156. In response to the collapsing of the bellows power piston 156, the silicone oil 81a within the bellows power piston 156 is displaced down connecting line 81 through a conducting passage in the steam vaporizer 118 to the hollow isolation piston 87 within the cylinder 85. In response thereto, the piston 87 is displaced downward, transmitting the work output of the engine 105 to the fluid isolation bellows 89, and thence to the hydraulic output line 105a. The hydraulic output may be appropriately coupled for producing useful work.

When the DC torque motor 129 is actuated with the opposite polarity by the control 129a, the bellows displacement piston 126 is lowered to its minimum height position, causing the water in this system to be drawn back so that'the surface level is within the steam condenser 114. The resultant decrease in steam pressure causes the synthetic mica piston 166 to drop'and, at the same time, expand the bellows power piston 156. As the piston 156 expands, the silicone oil 81a is drawn into the interior region of that piston and the mercury bellows piston 154 collapses. The collapsing of the bellows piston 154 is effective to withdraw the liquid mercury so that the liquid mercury level again is within the mercury condenser 144. The consequent condensation of mercury results in the depressurization of the high temperature portion of the engine 105. Thus, both component engines depressurize together, completing the cycle of operation of the engine 105.

As the cycle is repeated, the hydraulic output on the output 105a is pulsed synchronously at the repetition rate of the control signal applied to the DC torque motor 129. The work output of the engine 105 may be extracted by check valves coupled to the hydraulic line 105a, which valves may assure unidirectional flow of the output fluid. it will be noted that the output fluid is routed through the condenser 114 cooling jacket to remove the heat extracted from the condensing steam. Heat extracted from the condensing mercury is transmitted directly to to the steam vaporizer 118 by thermal conduction from the adjacent condenser 144. It will be understood that the mercury vapor is separated from the superheated steam by the mercury bellows power piston 165 but, since both are at the same-temperature (935 Fahrenheit), no heat is lost from the mercury vapor in the mercury bellows power piston 165. The synthetic mica piston insulator 166 retards the flow of heat from the mercury vapor and superheated steam (935 Fahrenheit to the silicone oil 81a (approximately 500 Fahrenteit) in the bellows pistons 156, thereby preventing the superheating of the steam in line 122a and the overheating of the silicone oil 81a. Pressure balancing of the power bellows is achieved using the saturated steam directly from the vaporizer 118 (342 Fahrenheit). Heat transferred to this steam from the silicone oil 81a (500 Fahrenheit) merely provides a portion of the superheat which the steam will eventually receive in the course of the cycle when the bellows piston 156 is collapsed and the steam is forced via the line 1221) to the superheater 122. To further recover the conductive heat transfer through the synthetic mica piston 166, the silicone oil 81a is routed through the vaporizer 118 as it passes on its way to the hollow isolation piston 87. In doing so, the conductive heat losses through the synthetic mica insulator piston 166 are utilized in vaporizer 118 and further, the parasitic losses through the isolation piston 87 are minimized.

Heat is added to the engine at the mercury vaporizer 148 at approximately 935 Fahrenheit. As the mercury power piston is collapsed-during the return stroke of a cycle, the mercury vapor passes through and provides the input heat for the steam superheater 122, which acts as a counter flow heat exchanger. Thus, the steam superheat is regenerated from the mercury vapor. Mercury vapor to liquid regeneration is achieved in the mercury tidal regenerator 146 with some of the heat being tapped off the hot end of this regenerator and passed via a thermally conductive path 91 to steam vaporizer 1 l8, contributing to the heat input of the low temperature portion of the engine 105.

Thus, it will be understood that, in addition to the utilization of the heat extracted in the mercury condenser 144 for regeneration and supplying the input heat to the low temperature engine, further regeneration techniques are used in the various other respective heating portions of the cycle of the engine 105. The overall effect of the regeneration provides for a substantially high efficiency factor approaching a value of 27 percent for practical temperatures and pressures. This compares with the 12 percent efficiency factor of a single cycle tidal regenerator engine which operates at similar pressures and temperature conditions. A substantial measure of the overall increased efficiency in the binary cycle tidal regenerator engine 105 is due to the high average temperature at which heat is added to the mercury cycle.

Further efficiency improvements may be achieved in accordance with the present invention by extending the binary cycle tidal regenerator heat engine to include additional cascaded, single cycle tidal regenerator engines, thereby forming a multiple cycle tidal regenerator having a plurality of single cycle tidal regenerator engines interconnected in a descending thermal series. The individual single cycle engines in a multiple cycle engine may be characterized by an input and output temperature, respectively, corresponding to the temperature at which heat is added and rejected. It will be understood that the range of temperature between the input and output temperatures for each of the engines are non-overlapping. In a descending thermal series, each engine, starting with the highest temperature component engine, rejects heat at a temperature higher than that at which the next lower engine in the series accepts heat. As an example, an engine similar to engine 40 may be added to the binary cycle engine of FIG. 1, forming a three cycle engine. In this example, the output line of the additional engine (similar to the line 52a) of the engine 40, couples into the common output line 5a. Further, the input line of the added engine (similar to the line 22b of the engine 40) couples into the line connecting the vaporizer 48 to the power cylinder 52 so that the working fluid vapor pressure of the engine 40 serves as a means to drive a displacement piston in the added engine in a manner similar to which the displacement piston 54 is driven in the engine 40 from the working fluid vapor pressure of the engine 10. In addition, the added component engine would also have a heat transfer means (similar to the heat transfer means 60 shown in FIG. 1) for transferring the rejected heat from the condenser of the added engine to the vaporizer 48 of the engine 40. It will be understood that the working fluid of the added engine has a vapor pressure lower than the vapor pressure of the working fluid in the engine 40, and that the range of temperatures in the added engine between the temperature at which heat is added and that at which heat is rejected lies above the corresponding range in the engine 40. Similarly the range of the engine 40 lies above the cone spending range of the engine 10. The operation of the added component engine is appropriately phased so that power generated by that engine is additively coupled to the output line 5a.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed is:

l. A binary cycle heat engine comprising: a first and second closed system, each of said systems having a characteristic output and input temperature, said output temperature being lower than said input temperature, and having a characteristic temperature range, said range including the temperatures between said output and inputtemperatures wherein said temperature ranges for said first and second systems are nonoverlapping, said first and second systems being arranged in a descending thermal series, wherein said range of said first system includes temperatures higher than those in said range of said second system, each one of said systems including:

l. a condensable vapor serving as a working fluid;

2. a tidal regenerator;

3. means for establishing a temperature gradient across said regenerator;

4. means for altematelyestablishing the level of said working fluid in its liquid phase at points of high temperature and at points of low temperature associated with said tidal regenerator, pressure being relatively high when said level is at said points of high temperature and relatively low when said level is at said points of low temperature;

means for extracting heat from said condensable vapor in said first sytem at'said points of low temperature; heat transfer means for transferring said heat extracted from said condensable vapor in said first sytem to said condensable vapor in said second system at said points of high temperature; and means responsive to changes in pressure communicating with said first and second systems for converting said changes to additive components of useful energy. r

2. A binary cycle heat engine as defined in claim 2,

further comprising a means for phasing the operation 14 of said systems to provide synchronous changes in pressure in each of said systems.

3. A binary cycle heat engine as defined in claim 1, wherein said condensable vapor in said first closed system has a vapor pressure substantially below thatof said condensable vapor in said second closed system.

4. A binary cycle heat engine as defined in claim 2, wherein said second closed system includes: a vaporizer, to which heat is applied, and a condenser, from which heat is extracted, disposed at opposite ends of said tidal regenerator, wherein said temperature gradient is established, said second closed system further comprising a control system for actuating said means for alternately establishing the level of said working fluid in said second system in its liquid phase, whereby said level is alternated substantially in said vaporizer and substantially in said condenser, said pressure in said second closed system being relatively high when said level is in said vaporizer and relatively low when said level is in said condenser.

5. A binary cycle heat engine as defined in claim 4,

wherein said first closed system includes: a vaporizer, to which heat is applied, and a condenser, from which heat is extracted, disposed at opposite ends of said tidal regenerato'r, whereby said temperature gradient is established, said system further comprising a control system for actuating said means for alternately establishing the level of said working fluid in said first system in its liquid phase, in response to said pressure changes in said second closed system,-whereby said level is alternated substantially in said vaporizer in response to said pressure being relatively high in said second system and substantially in said condenser in response to said pressure being relatively low in said second system, said pressure in said first closed system being relatively high when said level is in said vaporizer and relatively low when said level is in said condenser.

6. A heat engine as defined in claim 5, wherein said means in said second closed system for alternately establishing a level of said working fluid in its liquid phase at points of high temperature and at points of low temperature comprises a displacement cylinder for said working fluid, a reciprocatory displacement piston in said displacement cylinder, and means for actuating said displacement piston to move said working fluid through said engine.

7. A heat engine as defined in claim 6, wherein said means for actuating said displacement piston comprises a direct current torque motor, a ball screw and a ball nut.

8. A heat engine as defined in claim 5, wherein said means in said first closed system for alternately establishing a level of said working fluid in its liquid phase at points of high temperature and at points of low temperature comprises a displacement cylinder for said working fluid, a reciprocable displacement piston in said displacement cylinder, and means for actuating said displacement piston to move said working fluid through said engine.

9. A heat engine as defined in claim 8, wherein said means for actuating said displacement piston is directly responsive to said pressure in said second closed system.

10. A binary cycle heat engine as defined in claim 1, wherein said means responsive to changes of said pressure communicating with said first and second systems for converting said changes to. mechanical energy comprises a power cylinder and a reciprocatory power piston, said power piston being driven in a first direction by said relatively high pressures in said first and second systems and returning in the second direction against said relatively low pressures in said first and second systems. I MY l 1. A binary cyc l e heat engine as defined in claim 10, wherein said second closed system further comprises a second heating means at the vaporizer of said tidal regenerator for heating said working fluid associated with said second system, said second heating means being disposed between said vaporizer and said power cylinder.

12. A cascaded multiple cycle heat engine comprise ing: a plurality of closed systems, each of said closed systems having a characteristic output and input temperature, said output temperature being lower than said input temperature, and having a characteristic temperature range, said range including the temperatures between said output and input temperatures, wherein the characteristic temperature ranges for each of said systems are non-overlapping, said plurality of closed systems being arranged in a descending thermal series wherein the one of said systems having the highest output temperature is arranged first in said series and the others of said systems are arranged so that the input temperature of each system in said series is lower than the output temperature of the preceding one of said systems in said series, each one of said systems including:

l. a condensable vapor serving as a working fluid;

2. a tidal regenerator,

3. means for establishing a temperature gradient across said regenerator;

4. means for alternately establishing the level of said working fluid in its liquid phase at points of high temperature and at points of low temperature associated with said tidal regenerator, pressure being relatively high when said level is at said points of high temperature and relatively low when said level is at said points of low temperature;

5. means for extracting heat from said condensable vapor at said points of low temperature;

heat transfer means for transferring the extracted heat from each of said systems, excepting the last in said descending thermal series, to said condensable vapor in the next lower system in said descending series at said points of high temperature for said next lower system; and means responsive to changes in pressure communicating with each one of said plurality of systems for converting said changes to additive components of useful energy.

13. A cascaded multiple cycle heat engine as defined in claim 12 further comprising means for phasing the operation of said systems to provide synchronous changes in pressure in each of said systems.

14. A cascaded multiple cycle heat engine as defined in claim 12, wherein said condensable vapor in each closed system in said descending thermal series has a vapor pressure substantially below that of said condensable vapor in the adjacent closed system lower in said descending thermal series. 

1. A binary cycle heat engine comprising: a first and second closed system, each of said systems having a characteristic output and input temperature, said output temperature being lower than said input temperature, and having a characteristic temperature range, said range including the temperatures between said output and input temperatures wherein said temperature ranges for said first and second systems are non-overlapping, said first and second systems being arranged in a descending thermal series, wherein said range of said first system includes temperatures higher than those in said range of said second system, each one of said systems including:
 1. a condensable vapor serving as a working fluid;
 2. a tidal regenerator;
 3. means for establishing a temperature gradient across said regenerator;
 4. means for alternately establishing the level of said working fluid in its liquid phase at points of high temperature and at points of low temperature associated with said tidal regenerator, pressure being relatively high when said level is at said points of high temperature and relatively low when said level is at said points of low temperature; means for extracting heat from said condensable vapor in said first sytem at said points of low temperature; heat transfer means for transferring said heat extracted from said condensable vapor in said first sytem to said condensable vapor in said second system at said points of high temperature; and means responsive to changes in pressure communicating with said first and second systems for converting said changes to additive components of useful energy.
 2. a tidal regenerator;
 2. a tidal regenerator;
 2. A binary cycle heat engine as defined in claim 2, further comprising a means for phasing the operation of said systems to provide synchronous changes in pressure in each of said systems.
 3. A binary cycle heat engine as defined in claiM 1, wherein said condensable vapor in said first closed system has a vapor pressure substantially below that of said condensable vapor in said second closed system.
 3. means for establishing a temperature gradient across said regenerator;
 3. means for establishing a temperature gradient across said regenerator;
 4. means for alternately establishing the level of said working fluid in its liquid phase at points of high temperature and at points of low temperature associated with said tidal regenerator, pressure being relatively high when said level is at said points of high temperature and relatively low when said level is at said points of low temperature; means for extracting heat from said condensable vapor in said first sytem at said points of low temperature; heat transfer means for transferring said heat extracted from said condensable vapor in said first sytem to said condensable vapor in said second system at said points of high temperature; and means responsive to changes in pressure communicating with said first and second systems for converting said changes to additive components of useful energy.
 4. means for alternately establishing the level of said working fluid in its liquid phase at points of high temperature and at points of low temperature associated with said tidal regenerator, pressure being relatively high when said level is at said points of high temperature and relatively low when said level is at said points of low temperature;
 4. A binary cycle heat engine as defined in claim 2, wherein said second closed system includes: a vaporizer, to which heat is applied, and a condenser, from which heat is extracted, disposed at opposite ends of said tidal regenerator, wherein said temperature gradient is established, said second closed system further comprising a control system for actuating said means for alternately establishing the level of said working fluid in said second system in its liquid phase, whereby said level is alternated substantially in said vaporizer and substantially in said condenser, said pressure in said second closed system being relatively high when said level is in said vaporizer and relatively low when said level is in said condenser.
 5. A binary cycle heat engine as defined in claim 4, wherein said first closed system includes: a vaporizer, to which heat is applied, and a condenser, from which heat is extracted, disposed at opposite ends of said tidal regenerator, whereby said temperature gradient is established, said system further comprising a control system for actuating said means for alternately establishing the level of said working fluid in said first system in its liquid phase, in response to said pressure changes in said second closed system, whereby said level is alternated substantially in said vaporizer in response to said pressure being relatively high in said second system and substantially in said condenser in response to said pressure being relatively low in said second system, said pressure in said first closed system being relatively high when said level is in said vaporizer and relatively low when said level is in said condenser.
 5. means for extracting heat from said condensable vapor at said points of low temperature; heat transfer means for transferring the extracted heat from each of said systems, excepting the last in said descending thermal series, to said condensable vapor in the next lower system in said descending series at said points of high temperature for said next lower system; and means responsive to changes in pressure communicating with each one of said plurality of systems for converting said changes to additive components of useful energy.
 6. A heat engine as defined in claim 5, wherein said means in said second closed system for alternately establishing a level of said working fluid in its liquid phase at points of high temperature and at points of low temperature comprises a displacement cylinder for said working fluid, a reciprocatory displacement piston in said displacement cylinder, and means for actuating said displacement piston to move said working fluid through said engine.
 7. A heat engine as defined in claim 6, wherein said means for actuating said displacement piston comprises a direct current torque motor, a ball screw and a ball nut.
 8. A heat engine as defined in claim 5, wherein said means in said first closed system for alternately establishing a level of said working fluid in its liquid phase at points of high temperature and at points of low temperature comprises a displacement cylinder for said working fluid, a reciprocable displacement piston in said displacement cylinder, and means for actuating said displacement piston to move said working fluid through said engine.
 9. A heat engine as defined in claim 8, wherein said means for actuating said displacement piston is directly responsive to said pressure in said second closed system.
 10. A binary cycle heat engine as defined in claim 1, wherein said means responsive to changes of said pressure communicating with said first and second systems for converting said changes to mechanical energy comprises a power cylinder and a reciprocatory therein, said power piston being driven in a first direction by said relatively high pressures in said first and second systems and returning in the second direction against said relatively low pressures in said first and second systems.
 11. A binary cycle heat engine as defined in claim 10, wherein said second closed system further comprises a second heating means at the vaporizer of said tidal regenerator for heating said working fluid associated with said second system, said second heating means being disposed between said vaporizer and said power cylinder.
 12. A cascaded multiple cycle heat engine comprising: a plurality of closed systems, each of said closed systems having a cHaracteristic output and input temperature, said output temperature being lower than said input temperature, and having a characteristic temperature range, said range including the temperatures between said output and input temperatures, wherein the characteristic temperature ranges for each of said systems are non-overlapping, said plurality of closed systems being arranged in a descending thermal series wherein the one of said systems having the highest output temperature is arranged first in said series and the others of said systems are arranged so that the input temperature of each system in said series is lower than the output temperature of the preceding one of said systems in said series, each one of said systems including:
 13. A cascaded multiple cycle heat engine as defined in claim 12 further comprising means for phasing the operation of said systems to provide synchronous changes in pressure in each of said systems.
 14. A cascaded multiple cycle heat engine as defined in claim 12, wherein said condensable vapor in each closed system in said descending thermal series has a vapor pressure substantially below that of said condensable vapor in the adjacent closed system lower in said descending thermal series. 